Cannabinoid Testing Methods Explained
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A cannabinoid result is produced by an analytical process, not simply by placing a sample in an instrument. Sample preparation, calibration, separation, detection, and quality checks all contribute to the final number.
Understanding a few method names can make laboratory reports easier to read.
Liquid chromatography
Liquid chromatography separates substances carried through a column by a liquid mobile phase. High-performance liquid chromatography, or HPLC, is a common form of this technique.
Depending on the method, a laboratory can measure acidic and neutral cannabinoids separately. Detectors may measure light absorption or use mass spectrometry to help identify and quantify the separated compounds. NIST has published liquid-chromatography methods for measuring cannabinoids in hemp materials.
Gas chromatography
Gas chromatography separates compounds in a gas-phase system. Heat during analysis can affect acidic cannabinoids, so sample preparation and the method's treatment of those compounds matter when interpreting the result.
The instrument name alone does not tell a reader exactly which compounds were measured or how a reported total was calculated. The method description and report footnotes provide that context.
What makes a method dependable?
Important questions include whether the method is suitable for the sample type, whether it distinguishes the intended compounds, and whether calibration and quality-control checks support the measurement.
Reference materials provide known or assigned values that help laboratories evaluate their measurements. Interlaboratory comparison programs also help laboratories assess how their results compare with those of other participants. NIST's cannabis measurement work includes analytical methods, reference materials, and a laboratory quality-assurance program.
Comparing reports fairly
Before comparing two numbers, check the sample, compounds, units, reporting basis, and method. A result expressed as a calculated total should not be compared directly with a result for only one compound. Ask the laboratory to explain the relationship when the reports use different terminology.
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